10 BULLETIN 475, U. S. DEPARTMENT OF AGEICULTUEE. 
be to make the room, whether in a building or tent, as tight as pos- 
sible, except for the openings required for ventilation. All chinks 
should be closed completely. Wherever practicable as hot a fire 
should be kept up at night as during the day. This is particularly 
necessary in a tent, where any dying down of the fire at night causes 
the air to cool rapidly, with consequent delay and loss of time and 
labor. 
The stove is usually placed in the center of the room and approxi- 
mately level with the lowest tiers of trays. This results in much 
slower drying of the cones which are near the bottom of the room 
and at a distance from the stove. Attempts have been made to obvi- 
ate this difficulty hy dividing the stovepipe into sections and carry- 
ing it through as much of the room as possible, but without complete 
success. Better drying is secured in the farther ends of the room, 
but the bottom remains much cooler than the top. This difference is 
especially marked in tents, where cold air constantl}' passes in under 
the walls. With only one stove even distribution of heat is impossi- 
ble. W^ith stoves set at opposite ends of the tent and connected by a 
single stovepipe conditions are but little better. In one instance 
where this arrangement was used a difference of from 20° to 30° F. 
was found in the temperature of the air at the highest and lowest 
trays in a six-tier stack. 
One method of hastening the opening of the cones in the lower 
trays is to raise them as the drying proceeds and the cones in the 
upper trays are removed. This, however, requires additional han- 
dling and loss of time. A better method, wherever space is available, 
is to place the lowest tier of trays somewhat above the stove. Koom 
for air circulation is essential. The tiers of trays should be at least 
6 inches apart vertically, preferably 8 inches, and the same dis- 
tance from the walls. 
The best method of securing even distribution of heat, although 
not always practicable, is to have the drying room heated from 
below. If conditions permit, an excavation should be made under 
the building and the stove placed below the floor. This not only 
heats the room above more evenly, but furnishes additional space 
for spreading cones. The stovepipes should pass through as many 
parts of the dry room as possible. Still better results are obtained 
if hot-air pipes can be conducted from the drum of the stove into 
the room above, and even more heat can be made available by in- 
closing the stovepipes in jackets, which need not extend farther 
than the openings where the pipes pierce the floor. 
Maximum temperatures and duration of heating. — The degree of 
heat and the length of time required to open cones vary somewhat 
with different species, but still more with the conditions under 
